Environmental control system mixing cabin discharge air with bleed air during a cycle

ABSTRACT

A system and method that comprises an air cycle machine, a flow of bleed air, at least one heat exchanger, and an inlet configured to supply the flow of the bleed air is provided. The bleed air flows from a source to mix with recirculated air in accordance with a high pressure mode or a recirculation chilling mode. The system and method also can also utilize the recirculated air flowing from the chamber to drive or maintain the air cycle machine in accordance with the above modes.

BACKGROUND OF THE INVENTION

In general, there is an overarching trend in the aerospace industrytowards more efficient systems within an aircraft. With respect topresent air conditioning systems of the aircraft, efficiency can bederived from utilizing proper engine bleed pressures based onenvironmental condition surroundings the aircraft.

For example, pressurized air from an engine of the aircraft is providedto a cabin through a series of systems that alters the temperature,humidity, and pressure of the pressurized air. To power this preparationof the pressurized air, the only source of energy is the pressure of theair itself. As a result, the present air conditioning systems havealways required relatively high pressures at cruise. Unfortunately, inview of an overarching trend in the aerospace industry towards moreefficient aircraft, the relatively high pressures provide limitedefficiency with respect to engine fuel burn.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment, an environmental control system, comprisesan air cycle machine comprising a compressor and a turbine; a flow ofbleed air from a source; a first valve configured to control the flow ofthe bleed air; a flow of recirculated air from a chamber; and a secondvalve configured to control the flow of the recirculated air.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 depicts a schematic of a system according to an embodiment;

FIG. 2 depicts another schematic of a system according to an embodiment;

FIG. 3 depicts a high pressure mode schematic of a system aircraftaccording to an embodiment;

FIG. 4 depicts a low pressure mode schematic of a system aircraftaccording to an embodiment; and

FIG. 5 depicts a boost pressure mode schematic of a system aircraftaccording to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

As indicated above, the relatively high pressures provide limitedefficiency with respect to engine fuel burn. Thus, what is needed is anenvironmental control system, which eliminates a primary heat exchangerand uses cabin discharge air to power the cycle at altitude, to providecabin pressurization and cooling at high engine fuel burn efficiency.

In general, embodiments of the present invention disclosed herein mayinclude a system and/or method (herein system) comprising anenvironmental control system, which excludes a heat exchanger between anengine and an air cycle machine to create the lowest pressure drop pathpossible. The environmental control system provides a new approach tocabin air conditioning that, for example, can operate at pressures aslow as 2.5 psi below the cabin pressure.

FIG. 1 illustrates a medium (e.g., air) flowing through a system 100from an inlet 101 to a chamber 102, as indicated by solid-lined arrowsA, B. In the system 100, the medium can flow from the inlet 101 to acompressing device 120, from the compressing device 120 to a secondaryheat exchanger 130, and from the secondary heat exchanger 130 to thechamber 102. Further, the medium recirculates from chamber 102 throughthe system 100 and back to the chamber 102 (and/or external to thesystem 100), as indicated by the dot-dashed lined arrows D, E.

In one embodiment, the system 100 can be any environmental controlsystem of a vehicle, such as an aircraft or watercraft, that providesair supply, thermal control, and cabin pressurization for a crew andpassengers of the vehicle (e.g., a cabin air conditioning system of anaircraft). The system may also include avionics cooling, smokedetection, and fire suppression. For example, on an aircraft, air issupplied to the environmental control system by being “bled” from acompressor stage of a turbine engine. The temperature, humidity, andpressure of this “bleed air” varies widely depending upon a compressorstage and a revolutions per minute of the turbine engine. To achieve thedesired temperature, the bleed-air is cooled as it is passed through atleast one heat exchanger (e.g., exchanger 130). To achieve the desiredpressure, the bleed-air is compressed as it is passed through acompressing device (e.g., compressing device 120). The interaction ofthe environmental control system with the engine influences how muchfuel burn by the engine is needed to perform operations, such assupplying pressurized air, related to that interaction.

Heat exchangers (e.g., a secondary heat exchanger 130) are equipmentbuilt for efficient heat transfer from one medium to another. Examplesof heat exchangers include double pipe, shell and tube, plate, plate andshell, adiabatic wheel, plate fin, pillow plate, and fluid heatexchangers. Continuing with the aircraft example above, air forced by afan (e.g., via push or pull methods) is blown across the heat exchangerat a variable cooling airflow to control the final air temperature ofthe bleed-air.

The compressing device 120 (e.g., an air cycle machine as describedbelow) is a mechanical device that controls/regulates a pressure of amedium (e.g., increasing the pressure of a gas). Examples of acompressor include centrifugal, diagonal or mixed-flow, axial-flow,reciprocating, ionic liquid piston, rotary screw, rotary vane, scroll,diaphragm, air bubble compressors. Further, compressors are typicallydriven by an electric motor or a steam or a gas turbine.

Note that the system 100 of FIG. 1 is in contrast to a conventionalcabin air conditioning system that includes a traditional cabinthree-wheel air conditioning system. In the conventional cabin airconditioning system, high pressure air from, for example, an enginepasses through a in series a first ram air heat exchanger, an air cyclemachine, a second ram air heat exchanger, and a high pressure waterseparator where the air is cooled and dehumidified, such that theresulting cold dry air is used to cool the cabin, flight deck, and otherairplane systems. In operation, high-pressure high-temperature air fromeither then engine enters the first heat exchanger and is cooled by ramair. This warm high pressure air then enters the ACM compressor. Thecompressor further pressurizes the air and in the process heats it. Theair then enters the second heat exchanger and is cooled by ram air toapproximately ambient temperature. This cool high pressure air entersthe high pressure water separator where the air goes through thereheater, where it is cooled; the condenser, where it is cooled by airfrom the ACM turbine; the water extractor, where the moisture in the airis removed; and the reheater, where the air is heated back to nearly thesame temperature it started at when it entered the high pressure waterseparator. The warm high pressure and now dry air enters the turbine,where it is expanded and work extracted. The work from the turbine,drives both the before mentioned compressor and a fan that is used topull ram air flow through the first and second heat exchangers. Afterleaving the turbine, the cold air, typically below freezing, cools thewarm moist air in the condenser and is then sent to condition the cabinand flight deck.

The system 100 of FIG. 1 will now be described with reference to FIGS.2-5, in view of the aircraft example above. FIG. 2 depicts a schematicof a system 200 (e.g., an embodiment of system 100) as it could beinstalled on an aircraft. The system 200 illustrates bleed air flowingin at inlet 201 (e.g., off an engine of an aircraft at an initial flowrate, pressure, temperature, and humidity), which in turn is provided toa chamber 202 (e.g., cabin, flight deck, etc.) at a final flow rate,pressure, temperature, and humidity. Then the bleed air recirculatesback through the system 200 from the chamber 202 (herein recirculatedair and represented by the dot-dashed line) to drive the system 200. Thesystem in includes a shell 210 for receiving and directing ram airthrough the system 200.

The system 200 further illustrates a secondary heat exchanger, 220, anair cycle machine 240 (that includes a turbine 243, a compressor 244, aturbine 245, a turbine 247, a fan 248, and a shaft 249), a reheater 250,a condenser 260, and a water extractor 270, each of which is connectedvia tubes, pipes, and the like. Note that based on the embodiment, anexhaust from the system 200 can be sent to an outlet (e.g., releases toambient air).

The system 200 is an example of an environmental control system of anaircraft that provides air supply, thermal control, and cabinpressurization for the crew and passengers of the aircraft. Valves aredevices that regulate, direct, and/or control a flow of a medium (e.g.,gases, liquids, fluidized solids, or slurries, such as bleed-air) byopening, closing, or partially obstructing various passageways withinthe tubes, pipes, etc. of the environmental control system 200. Valvescan be operated by actuators, such that the flow rates of any medium inany portion of the environmental control system 200 may be regulated toa desired value. A secondary heat exchanger 220 is an example of a heatexchanger as described above.

The air cycle machine 240 (e.g., the compressing device 120), whichincludes a turbine 243, compressor 244, another turbine 245, anotherturbine 247, a fan 248, and a shaft 249, controls/regulates atemperature, a humidity, and a pressure of a medium (e.g., increasingthe pressure of a bleed air). The compressor 244 is a mechanical devicethat raises the pressure of the air received. The compressor 244 isconfigured to, whether during a low pressure mode (e.g., at altitude), ahigh pressure mode (e.g., on ground), recirculation chilling mode, orpressure boost mode, pressurize the recirculated air discharging fromthe chamber 202 to match or closely match a pressure of the bleed air.The turbines 243, 245, 247 are mechanical devices that drive thecompressor 244 and the fan 248 via the shaft 249. The fan 248 is amechanical device that can force via push or pull methods air throughthe shell 210 across the secondary heat exchanger 220 at a variablecooling airflow. Thus, the turbines 243, 245, 247, the compressor 244,and the fan 248 together illustrate, for example, that the air cyclemachine 240 may operate as a five-wheel air cycle machine that utilizesair recirculated from the chamber 202.

The reheater 250 and the condenser 260 are particular types of heatexchanger. The water extractor 270 is a mechanical device that performsa process of taking water from any source, such as bleed-air, eithertemporarily or permanently. Together, reheater 250, the condenser 260,and/or the water extractor 270 can combine to be a high pressure waterseparator.

Note that in the environmental control system 200 of FIG. 2 there is no‘primary’ heat exchanger. In this way, the environmental control system200 shows a new approach to cabin air conditioning (e.g., chamber 202)that can operate at relatively low pressures compared to conventionalsystems (e.g., operate at 2.5 psi below a cabin pressure). That is, theenvironmental control system 200 eliminates the ‘primary’ heat exchangerand utilizes recirculated air from the chamber 202 (e.g., uses cabindischarge air) to power the air cycle machine 240 at altitude. In turn,when the environmental control system 200 is combined with a three portbleed system, the direct path between the engine and the air cyclemachine creates a lowest pressure drop path possible.

The arrows of FIG. 2 illustrate all the possible paths that the bleedair and the recirculated air may flow through the environmental controlsystem 200, as directed by the valves. Embodiments of depictingdifferent combinations of flow paths will now be described with respectto FIGS. 3-5.

FIG. 3 depicts a schematic of a system 200 operating in the highpressure mode (e.g., an operational embodiment of the system 200 of FIG.2). The flow of bleed air is illustrated as solid arrows flowing throughthe system 200 from inlet 201 to chamber 202. The flow of recirculatedair is illustrated as dot-dashed arrows flowing from the chamber 202through the system 200. This mode of operation can be used at flightconditions when a pressure of air from a source (e.g., an engine and/orthe APU) is adequate to drive a cycle of the system 200 or when achamber 202 temperature demands it. For example, conditions such asground idle, taxi, take-off, climb, descent, hold, and like conditionswould have the air cycle machine 240 operating in a high pressure mode.Further, extreme temperature high altitude cruise conditions couldresult in one or of the more air cycle machines 240 operating in thismode.

In operation, recirculated air flows from the chamber 202 and enters thecompressor 244. The compressor 244 further pressurizes the recirculatedair and in the process heats it. Further, bleed air, such ashigh-pressure high-temperature air, from a source (e.g., an engineand/or the APU) flows from the inlet 201, through a turbine 247, and,downstream of the compressor 244, mixes with pressurized and heatedrecirculated air. In this way, the bleed air from the source via theinlet 201 is conditioned by the turbine 247 of the air cycle machine 240before being mixed with the recirculated air (e.g., expanded across theturbine 247). The mixed air then enters the secondary heat exchanger 220and is cooled by ram air of the shell 210 to approximately an ambienttemperature. Due to this mixing, a pressure of the recirculated airdischarging from the compressor 244 is managed by the compressor 244 tomatch or closely match a pressure of the bleed air discharging from theturbine 247. This cool high pressure mixed air exits the secondary heatexchanger 220 and enters the high pressure water separator.

Note that in conventional aircraft systems, air being supplied to acabin is produced from a process performed by a mix chamber. The mixchamber mixes bleed air from a pack (e.g., an air cycle machine), whichis at a first temperature, and recirculated air from the cabin, which isat a second temperature, to provide to the cabin with conditioned air.In contrast, the operational embodiment of the high pressure modeconditions the recirculated air and the bleed air from the sourcetogether inside the air cycle machine 240 to produce the cool highpressure mixed air, thereby eliminating the need for a mix chamber.

In the high pressure water separator, the cool high pressure mixed airgoes through the reheater 250, where it is cooled; the condenser 260,where it is cooled by air from the turbine 243 of the air cycle machine240; a water extractor 270, where the moisture in the air is removed;and the reheater 250, where the air is heated back to nearly the sametemperature it started at when it entered the high pressure waterseparator. The warm high pressure and now dry air enters the turbine243, where it is expanded so that work can be extracted. The work fromthe turbine 243 can drives both the before mentioned compressor 244 anda fan 248 that can be used to pull ram air flow through the shell 210and across the secondary heat exchanger 220. After leaving the turbine243, the air is cold, such as below freezing. This cold air is utilizedto cool the warm moist air in the condenser 260 before being sent to thechamber 202 (e.g., to condition a cabin and a flight deck of theaircraft).

Note that, in extreme temperature high altitude cruise conditions (e.g.,when the aircraft is at cruise, such as above 30,000 or 40,000 feet),the cool high pressure mixed air may upon exiting the secondary heatexchanger 220 bypass the high pressure water separator and directlyenter the chamber 202. In this case, the recirculated air from thechamber may be utilized to drive the turbine 245 and prevent the aircycle machine 240 from windmilling (i.e., turning below a minimum speed,such as 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, etc.revolutions per minute). That is, the recirculated air is taken from thechamber 202, expanded across the turbine 245, and dumped into the shell210 based on a pressure ratio between ambient air of the shell 210 andthe recirculated air. Other examples of mechanism that preventwindmilling include an electric fan, a break, fan bypass, etc.

FIG. 4 depicts a schematic of a system 200 operating in therecirculation chilling mode (e.g., an operational embodiment of thesystem 200 of FIG. 2). The flow of bleed air is illustrated as solidarrows flowing through the system 200 from inlet 201 to chamber 202. Theflow of recirculated air is illustrated as dot-dashed arrows flowingfrom the chamber 202 through the system 200. This mode of operation canbe used at flight conditions when a pressure of air from a source (e.g.,an engine and/or the APU) is adequate to drive a cycle of the system 200or when a chamber 202 temperature demands it. This mode of operationwould be used at flight conditions where a pressure of the air from asource (e.g., an engine and/or the APU) enters the air cycle machine 240at or approximately at 1 to 3 psi or above a pressure of the chamber202. For example, the mode may be utilized in such conditions as whenthe aircraft is at cruise (e.g., at altitudes above 30,000 or 40,000feet) and at or near standard ambient day types.

In operation, recirculated air flows from the chamber 202 and enters thecompressor 244. The compressor 244 further pressurizes the recirculatedair and in the process heats it. Further, bleed air, such ashigh-pressure high-temperature air, from a source (e.g., an engineand/or the APU) flows from the inlet 201 and, downstream of thecompressor 244, mixes with pressurized and heated recirculated air. Inthis way, the bleed air from the source via the inlet 201 bypasses theair cycle machine 240 entirely. The mixed air then enters the secondaryheat exchanger 220 and is cooled by ram air of the shell 210 toapproximately an ambient temperature. Due to this mixing, a pressure ofthe recirculated air discharging from the compressor 244 is managed bythe compressor 244 to match or closely match a pressure of the bleedair. This cool high pressure mixed air exits the secondary heatexchanger 220, bypasses the high pressure water separator, and entersthe chamber 202. In the case, recirculated air is used to keep the aircycle machine 240 turning at or above the minimum speed usingrecirculated air to drive turbine 245.

FIG. 5 depicts a schematic of a system 200 operating in the pressureboost mode (e.g., another operational embodiment of the system 200 ofFIG. 2). The flow of bleed air is illustrated as solid arrows flowingthrough the system 200 from inlet 201 to chamber 202. The flow ofrecirculated air is illustrated as dot-dashed arrows flowing from thechamber 202 through the system 200. This mode of operation can be usedat flight conditions when a pressure of the air from the source andentering the air cycle machine 240 is lower than a pressure of thechamber 202 (e.g., at or below 1, 1.5, 2, 2.5, 3, 3.5, etc. pounds persquare inch). For example, the mode may be utilized in such conditionsas when the aircraft is at cruise (e.g., at altitudes above 30,000 or40,000 feet) and at or near standard ambient day types.

In operation, the bleed air from the source via inlet 201 mixes with aportion of the recirculated air to produce mixed air. The mixed air thenenters the compressor 244 and is compressed and heated. This pressurizedwarm mixed air then enters the secondary heat exchanger 220 and iscooled by ram air of the shell 210 to a temperature desired for thechamber 202. The air then goes directly into the chamber 202.

Further, another portion of the recirculated air is used to provideenergy to the compressing and heating of the mixed air. That is, theanother portion of the recirculated air enters and expands across theturbine 245, so that and work is extracted. This work is enough to turnthe air cycle machine 240 at a speed required by the compressor 244 toraise a pressure of the mixed air from the source via inlet 201 to apressure that enables the mixed air to get through the secondary heatexchanger 220 and into the chamber 202. Note that the recirculated airexiting the turbine 245 is then dumped overboard through the shell 210.

The technical effects and benefits of embodiments of the presentinvention include providing an air cycle machine that is as efficient inthe pressure boost mode and the high pressure mode. For example, in theembodiments described above, a compressor in the high pressure mode thatcan have an input pressure of 14.7 psi, while in the pressure boost modethe compressor inlet pressure can be 8.5 psia. In turn, choosing acompressor flow in the high pressure mode, the compressor range can benarrowed to align the compressor operating points and achieve betterefficiency in the pressure boosting mode.

Aspects of the present invention are described herein with reference toflowchart illustrations, schematics, and/or block diagrams of methods,apparatus, and/or systems according to embodiments of the invention.Further, the descriptions of the various embodiments of the presentinvention have been presented for purposes of illustration, but are notintended to be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. An environmental control system, comprising: anair cycle machine comprising a compressor, a first turbine, and a secondturbine, each of which is located on a shaft of the air cycle machine; aflow of bleed air from a source; a first valve configured to control theflow of the bleed air with respect the air cycle machine in accordancewith a high pressure mode, a recirculation mode, and a pressure boostmode; a flow of recirculated air from a chamber; and a second valveconfigured to control the flow of the recirculated air with respect theair cycle machine in accordance with the high pressure mode, therecirculation mode, and the pressure boost mode, wherein theenvironmental control system is configured to operate in the highpressure mode comprising the first valve causing the flow of the bleedair to directly enter the first turbine, the second valve causing theflow of the recirculated air to directly enter the first compressor, andthe bleed air expanding across the first turbine to drive the firstcompressor, wherein the environmental control system is configured tooperate in the recirculation chilling mode comprising the first flowvalve causing the flow of the bleed air to bypass the air cycle machineand the second valve causing a first portion of the flow of therecirculated air to directly enter the compressor and a second portionof the flow of the recirculated air to directly enter the secondturbine, and wherein the environmental control system is configured tooperate in the pressure boost mode comprising the first flow valvecausing the flow of the bleed air to directly enter the compressor, andthe second valve causing the flow of the recirculated air to directlyenter the second turbine, wherein the second portion of the recirculatedair expands across the second turbine based on an energy ratio to turn ashaft of the air cycle machine, and wherein a pressure of therecirculated air exiting from the compressor matches a pressure of thebleed air bypassing the air cycle machine.
 2. The environmental controlsystem of claim 1, wherein a pressure of the recirculated air exitingfrom the compressor matches a pressure of the bleed air exiting from theturbine.
 3. The environmental control system of claim 1, wherein therecirculated air exiting from the compressor and the bleed air exitingfrom the first turbine are mixed to produce mixed air.
 4. Theenvironmental control system of claim 3, further comprising: at leastone heat exchanger, wherein the mixed air is provided to the at leastone heat exchanger.
 5. The environmental control system of claim 3,further comprises: a high pressure water separator configured tocondition the mixed air to produce the condition air; and a thirdturbine of the air cycle machine configured to receive the condition airfrom the high pressure water separator, wherein as the condition airexpands across the third turbine, work is extracted by the air cyclemachine to compress the recirculated air via the compressor.
 6. Theenvironmental control system of claim 1, wherein as the second portionof the recirculated air expands across the second turbine, work isextracted by the air cycle machine to compress the first portion of therecirculated air via the compressor.
 7. The environmental control systemof claim 1, wherein as the second portion of the recirculated airexpands across the second turbine, work is extracted by the air cyclemachine to compress the bleed air via the compressor.
 8. Theenvironmental control system of claim 1, wherein the environmentalcontrol system is of an aircraft.